The present invention pertains to a signal processing apparatus for ultrasound transducers, and to an ultrasound receiver apparatus. More particularly, the present invention directed to improving the signal received by such apparatus.
Ultrasound receiver may be used, for example, for non-destructive materials testing of tubes, wires or belts, by generating an ultrasound wave in the test object, e.g. by means of a piezo-electric test head or, for non-contact applications, by means of an electromagnetic acoustic transducer (EMAT). The emitted ultrasound signal is then picked up by the ultrasound receiver and converted into an output signal. Information about flaws in the material of the test object is detected in the pattern of the output signal. However, for EMATs, the problem from the beginning has been that the amplitude of the ultrasound signal produced is very small, because an EMAT has about 10% of the effectiveness of a piezoelectric transducer. The remedy has been to use costly, more powerful transmitters.
In particular, the ultrasound receivers used for non-destructive testing are beset by serious environmental signal distortion problems. Strong interference signals caused by the drives of the rolling frame in a rolling mill are generated during testing the material. These interference signals interfere also with the ultrasound signal, and with the processing of the ultrasound signal into an output signal. Such interference effects reduce the interpretability of the detection signal. In some instances, this makes meaningful analysis of the signal impossible.
In the past, attempts were made to shield the analog electric equipment following the ultrasound transducers against such interference. However, such shields are costly. Moreover, the installation space is limited in immediate proximity to the ultrasound transducer in many areas of their application. For that reason, the ultrasound transducer is typically separated from the subsequent analog electrical detection circuits. As a result of these inalterable spatial circumstances, it was necessary to date to connect the ultrasound transducer to the electronic evaluation assembly by a cable of a length of up to 30 m. Still these cables, as well as the electronic evaluation assembly, are exposed to strong interference signals in their working environment so that it has not been possible to date to generate signals having a large separation between the signal- and interference and a large signal-to-noise ratio.
It would therefore be desirable and advantageous to provide an improved ultrasound receiver to obviate prior art shortcomings and to exhibit great signal-to-noise ratio and great wanted-to-unwanted signal ratio.